This invention pertains to vertebral stabilization. Specifically, the invention is directed to vertebral implants and rod systems for stabilization of vertebral bodies and includes apparatuses and methods for temporary fixation until final alignment is established for permanent fixation.
Chronic back problems cause pain and disability for a large segment of the population. In many cases, the chronic back problems are caused by intervertebral disc disease and loss of stability of the intervertebral joint. Stabilization and/or arthrodesis of the intervertebral joint can reduce the pain and debilitating affects associated with disc disease.
Spinal stabilization systems and procedures have been developed to stabilize diseased intervertebral joints and, in some cases, to fuse the vertebrae that are adjacent to the diseased joint space. One type of spinal stabilization system includes bone implants and rods that are used for many types of spinal conditions including, for example, degenerative disc disease, scoliosis, spondylolithisis, spinal stenosis, etc. Examples of some spinal stabilization systems are disclosed in U.S. Pat. Nos. 6,010,503; 5,946,760; 5,863,293; 5,554,157; 5,549,608; and 5,190,543, the entire disclosures of which are incorporated herein by reference. In these systems, a bone implant (e.g., pedicle screw, bone hook) is typically anchored to each vertebral body to be stabilized and a connecting rod mounted to each implant to fix the vertebrae in a particular position.
In many known stabilizing systems, after the implant is positioned in or on the bone, a connecting rod is mounted and secured to the implant by, for example, a locking nut that fixes the rod in position as the nut is tightened. Often times adjustment of the position of the vertebrae (e.g., compression, distraction, rotation, etc.), the implant or the rod necessitates repeated loosening and retightening of the locking nut until a satisfactory position is achieved. However, repeated loosening and tightening of the locking nut not only adds additional steps to the surgical procedure, and thus can increase the duration of the surgery, but the long term integrity of the implant, rod or implant assembly can potentially be compromised due to repeated threading and unthreading of the nut before arriving at a satisfactory final position.
Accordingly, there is a continuing need for instrumentation and procedures that enhance the ease of performing positional corrections, reduce surgical time and preserve the integrity of the implanted system to reduce the likelihood of post-operative complications. The present invention is directed to addressing these needs.
The invention is directed to temporary spinal fixation apparatuses and methods for temporarily fixing the relative position of vertebral bodies or spinal implants until a permanent fixation position is determined. The disclosed apparatuses and methods can enhance the ease of placement of spinal implant assemblies, facilitate the accuracy of positioning of spinal vertebrae and preserve the integrity of the fixation system.
It will be noted that in several places throughout the specification, guidance is provided through lists of examples. In each instance, the recited list serves only as a representative group. It is not meant, however, that the list is exclusive.
In one embodiment, a surgical instrument of the invention includes a temporary fixation device having a proximal end, a distal end and a fixing member passed within the lumen of an inner cannula that is passed within the lumen of an outer cannula. According to this embodiment, the fixing member can be axially mobile within the lumen of the inner cannula and the inner cannula axially mobile within the lumen of the outer cannula. The distal end of the instrument provides for mounting to a portion of the spinal implant assembly and the proximal end can be used for operating the device.
In another embodiment, a surgical instrument according to the invention can include an anti-torque device to reduce the amount torque applied to spinal vertebrae while performing a spinal implant procedure.
In another embodiment, a surgical instrument of the invention can be contained in a kit including temporary fixation devices having various inner and outer cannula lengths, various sized spinal implants, or other instruments used to perform a surgical procedure according to the invention.
The invention also provides methods for stabilizing the spinal column utilizing the instruments and principles disclosed herein.